The Department of Labor’s Monthly Labor Review features an 18-page report about work-related multiple-fatality incidents (pdf). While 9 out of every 10 work-related accidents that result in death involve a single fatality, between the study years of 1995 and 1999, 10 percent of the fatal events involved multiple deaths.
There were 1,109 incidents resulting in 2.949 deaths during the study years. Almost three quarters of these incidents involved two fatalities per event, but the nine worst catastrophes claimed a total of 266 workers